1. Field of the Invention
The present invention relates generally to centrifugal processing systems with rotors adapted to hold semiconductor articles, such as wafers or other semiconductor microelectronic articles.
2. Background
During the fabrication of flat media, such as microelectronic and semiconductor articles, various manufacturing steps involve the application of processing liquids and gases to the articles being processed. The application and removal of these processing fluids to and from the exposed surfaces of the workpieces or articles is enhanced by spinning movement of the articles within the processing chamber. Centrifugal action helps to apply fluids on the surfaces being processed.
As one example, after a flat media article has been cleaned, it must be dried. Any water droplets or other cleaning fluid that remain have at least some potential of leaving a residue or particles which may interfere with subsequent operations or cause defects in the resulting electronic products. As with most manufacturing operations relating to semiconductors and microelectronic devices, having an exceptionally clean environment, substantially free of particles, residues, etc., is a critical factor. Spinning the articles helps remove water or other processing liquids, so that such residues or particles are less likely to remain. Spinning also reduces processing time as droplets are physically removed via centrifugal force.
In the centrifugal processing machine described in the U.S. Pat. No. 5,784,797, incorporated by reference, the articles are held in a rotor that includes a rotor frame for holding the articles in an array, without an article carrier. The rotor has retainers which contact the articles to hold them in place. While this type of design may have met with varying degrees of success, several disadvantages remain. Specifically, contaminant particles may be created by the interaction of the edges of the articles, and the rotor surfaces supporting them.
Post-process analyses of the articles (semiconductor wafers), processed in a machine as described above, show residue signatures of carbon and fluorine, and in some cases chlorine. The residues were also present on the device side of the wafers, with the highest defect density near the edges of the wafers. This residue generation is caused by the relative clocking motion between the wafers and the rotor. This motion produces kinetic friction at the contact interfaces, causing the wafer edges to abrade, and wear on the thermoplastic rotor combs.
Therefore, there is a need for an improved machine to reduce or eliminate the creation, deposition and redistribution of residues and particles.
In a first aspect of the invention, a contact bar of a lockdown mechanism approaches the articles or wafers in a rotor with a trajectory that is largely normal to the edge of the wafers. This reduces or eliminates sliding contact at the edges of the articles and hence reduces particle generation.
In another, separate aspect of the present invention, improved combs include a plurality of projections and a rod or strip made from a resilient material. While the teeth of the combs guide and hold the articles, the resilient rod allows the articles to be better secured into the rotor, with less risk of damage.
Accordingly, it is an object of the invention to provide an improved rotor for use in processing semiconductor articles.
This and further objects and advantages will be apparent to those skilled in the art in connection with the drawings and the detailed description of the preferred embodiment set forth below.